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Original article

Correction of severe post-traumatic kyphosis by posterior vertebra column resection

ZHANG, Xue-song; ZHANG, Yong-gang; WANG, Zheng; CHEN, Chao; WANG, Yan

Editor(s): HA, O Xiu-yuan

Author Information
doi: 10.3760/cma.j.issn.0366-6999.2010.06.008
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Abstract

Spine trauma is a common event in modern society. Each year approximately 50 000 spinal column injuries occurred in US, excluding osteoporotic spinal fractures.1 Post-traumatic kyphosis is a common potential complication of spinal injury and poses one of the greatest challenges in spinal surgery, especially in the treatment of severe post-traumatic kyphosis.

Patients with focal kyphotic deformity equal to or greater than 30° have an increased risk of chronic pain in the region of focal kyphotic deformity2-4 or neurologic deficit. The sharp angular character of the deformity needs to be evaluated and treated differently from smooth kyphosis. Focal deformity correction is important because it can affect overall sagittal balance. Stiff or inflexible post-traumatic deformities are more difficult to correct and often require an osteotomy. The most common osteotomy techniques used are the Smith-Petersen osteotomy (SPO) and pedicle subtraction osteotomy (PSO). Surgical approaches include a combined anterior/posterior approach and an all posterior approach.2-4

Even though a lot of papers illustrated the techniques and clinical results of the correction of sagittal deformity, few of them focused on how to correct severe post-traumatic kyphosis with the effective regional deformity (ERD) of 60° or more. Posterior vertebra column resection (VCR) was a more aggressive and more challenging procedure than other osteotomy techniques. In sharp angular kyphosis and rigid deformity, VCR may achieve more correction and better functional improvement and back pain relief. In the present study, we retrospectively evaluated the clinical and radiographic results of posterior VCR with instrument fusion in the correction of severe post-traumatic kyphosis.

METHODS

Patients

From May 2004 to May 2006, 53 patients (38 male, 15 female) at an average age of 37.6 years (range, 24 to 66 years), were surgically treated for symptomatic post-traumatic thoracolumbar kyphosis with a posterior wedge closing osteotomy at our hospital. Among them, 5 consecutive adult patients with severe post-traumatic kyphosis were included in this study. Inclusion criteria of this study: (1) symptomatic post-traumatic thoracolumbar kyphosis; (2) ERD >60° and still worsening with or without neurological defect; (3) no osteoporosis, no endocrine or metabolic diseases. Five patients (4 male, 1 female), average 36 years old (22 to 59 years) were included in this study. The average delay between initial fracture and kyphosis correction was 16.4 years (7.0-27.5) years.

Case 1 underwent a posterior Harrington rods combined sublamina wire fixation and bone graft fusion soon after injury. The implants were removed 2 years later. No further injury occurred in the next 20 years until this admission, but the kyphosis gradually progressed and the patient presented with back pain. Urination problems started two years previous. Pseudarthrosis at the apex region could be seen in her 3-dimensional (3D) reconstruction images.

Case 2 had previously undergone an autologous bone graft (posterior iliac crest) fusion with brace control for six months after the injury and then returned to work for the next 20 years. However, he had to stop his job due to significant back pain and kyphosis five years previously. In the last two years he felt progressive weakness of both lower extremities and numbness in the saddle area and could not control his urination well.

Case 3 was a 20-year-old patient who suffered from a high drop accident when he was five years old. He returned to normal life three months after conservative treatment. On this admission, he complained of back pain and obvious weakness of the right thigh.

Case 4 was a high-drop injured patient who had accepted posterior lamina decompression and lateral fusion with long segmental pedicle screw fixation immediately after the accident. Unfortunately, a deep wound infection occurred three months after surgery that had not been controlled by debridements. Therefore, all the implants were removed 1.5 years after the prior procedure and a brace was used for six months. In the last five years, kyphosis and back pain became gradually more severe, but no neurological defect presented.

Case 5 was a miner who suffered incomplete paralysis due to heavy crush accident. After three years of conservative treatment, he could walk with a cane, but gradually worsening kyphosis and back pain posed upon his walking ability for the next eight years.

Radiological assessment

Radiographic documentation was made on the basis of standing anterior-posterior (AP) and lateral views, flexion and extension lateral views, and 3D computed tomographic (CT) scans. Magnetic resonance imaging was carried out to confirm the spinal canal influence. Radiographs were analyzed at three time-points: preoperatively, postoperatively, and at the latest follow-up. Regional angulation (RA) at the level of the deformity was drawn between the superior end plate of the adjacent cranial vertebra and the inferior end plate of the adjacent-caudal vertebra (positive value for kyphosis and negative value for lordosis). At each level, the ERD used to evaluate deformity was defined by subtracting the physiological RA for the level (Table 1), as reported by Stagnara et al,5 from the measured RA (ERD=RA-physiological RA for the level). Assessment of radiological fusion at follow-up was based on the presence of trabecular bone bridging at the osteotomy site according to Brantigan et al.6

Table 1
Table 1:
Physiological RA for each level according to Stagnara (1982)

Surgical technique

All surgeries were performed under motor evoked potential monitoring. No preoperative embolization of the affected vertebra was performed. A Maquet operation table was used. Under general anesthesia the patient was placed in a prone position, the incision was made through a straight posterior midline centered at the site of the apex of the deformity and extended above and below three levels. With intraoperative radiograph controls, three pairs of pedicle screws were inserted into the vertebrae which were cephalic or caudal accordingly with free-handed fashion. Multi-direction screws were recommended for use in order to avoid sagittal translation at the VCR site during correction (Figure 1).

Figure 1.
Figure 1.:
Pedicle screws were inserted into the vertebrae which were cephalic or caudal according to the apex vertebrae with free-handed fashion.Figure 2. Trans-pedicle decancellous procedure was performed, from both lateral sides to remove lateral cortical bone. The wedge resection was enlarged by removing upper and lower discs.

Expose both the lateral aspects of the target vertebral body with a sponge stick or periosteal elevator, then a trans-pedicle decancellous procedure, just like an "egg shell" technique was performed. A high-speed drill or curretage was used from both lateral sides to remove lateral cortical bone. A rongeur was used to create an "operational window" and protect the nerve root at the same level. The cancellous bone was saved for bone graft. The medial wall of the pedicle should be preserved during drilling to prevent neural cannal (Figure 2).

The wedge resection was enlarged by removing upper and lower discs until only a small part of cortical bone of the anterior vertebra body remained. Then all the posterior elements were removed to achieve a thin cortical bone around the spinal cord (Figure 3). In revision cases, normal dura was exposed by performing a laminectomy at a level adjacent to the previous decompression. A plane between the dura and the adjacent scar tissue was created. The scar which adhered to the dura in the area of the intended osteotomy was removed to avoid compression of the neural elements when closing the wedge space. Temporary rod fixation was used on the support side. Then the upper injured disc and endplate cartilage were removed. Care was taken to protect the nerve root at the same level. The remaining cortical walls (including lateral and anterior parts) were removed. Great care was taken not to injure the segmental vessels. The same procedure was carried out under the periosteal and annular fibrosus, and from the other side.

Figure 3.
Figure 3.:
A small part of cortical bone of the anterior vertebra body remained. Then most of the posterior elements were removed to achieve a thin cortical bone around the spinal cord.Figure 4. The surrounding thin cortical bone shell was opened from the lateral side of the cord canal, then from the posterior, and finally from the anterior.Figure 5. After VCR of the apex region, change a less contoured temporary rod, achieved a partial correction of the kyphosis, and a big space still can be found in the VCR region.

The surrounding thin cortical bone shell was opened from the lateral side of the cord canal, then from the posterior, and finally from the anterior. An Epstein reverse-cutting curette can be used to remove the shell of bone adjacent to the dural tube (Figure 4).

A second temporary rod, contoured to fit the shape of the deformity, was then inserted into the working side and secured into place. Then the previous rod was removed to facilitate complete removal of any residual bone or disc on that side (Figure 5).

An anterior PEEK cage or allograft structural support filled with saved cancellous bone was inserted into the right place under fluoroscopy. The osteotomy space was closed gradually. The sagittal correction axis was located at the middle or posterior vertebra (structural support site), a closing and opening procedure was done (Figure 6).

Figure 6.
Figure 6.:
Anterior structural support was inserted into the right place under fluoroscopy. The osteotomy space was closed gradually.Figure 7. A 66-year-old man (case 2) had undergone T12-L2 posterior fusion 27.5 years before. He developed significant back pain and kyphosis five years ago. In the recent two years, he felt progressive weakness of both lower extremities and numbness in the saddle area and could not control his urination. By preoperative CT-3D reconstruction of local deformity, we find that even posterior bony fusion mass cannot prevent development of local kyphosis (A). Sagittal CT scan show a focal kyphosis of 72° ERD in the thoracolumbar region and anterior bone bridging at the injured vertebra (B). MRI illustrates a sharp angular posterior portion of the vertebra impinges on the spinal cord (C). This patient underwent L1 vertebra coloumn resection during which bilateral T12 ribs were removed in our hospital. The images presented is his standing AP and lateral X-ray are two years postoperatively. Stable anterior bony fusion can be found, and a focal kyphosis ERD of 72° before operation had improved to 8° at final follow-up (D).

Clinical assessment

Operating time, average operative and postoperative blood loss, functional improvement, and all complications were documented, including early postoperative and late postoperative events. Clinical outcome was measured with the Oswestry disability index (ODI), back pain was evaluated preoperatively using a visual analog scale (VAS) and at two years postoperatively. Significant elements of the clinical history and outcomes were noted.

Statistical analysis

Normality was assumed and significance was set at P <0.05. Data before and after operation were analyzed with pairwise t test using statistical software SPSS 11.5 (SPSS Inc., USA).

RESULTS

The mean operating time was 265 minutes (220-408 minutes), with an average blood loss of 1362 ml (870-2570 ml). Complications occurred in two patients. Case 1 had a transient weakness of the left side lower extremity; the symptom improved spontaneously within one month without further treatment. Case 3 suffered a deep wound infection three weeks after operation; he recovered well by additional debridement, continuous perfusion and drainage.

Each patient finished at least two years of follow-up. The average ERD significantly decreased from 69° (58° to 86°) preoperatively to 4° (1° to 8°) after surgery (P=0.017) with a mean correction of 65°. ERD averaged 10.4° (7° to 17°) at the latest follow-up with a mean loss of 6.4°. VAS and ODI scores improved from a preoperative 7.4 (6.0 to 9.0) and 55.2 (48.0 to 60.0) to an average of 2.3 (1.0 to 4.0) and 12.2 (7.0 to 18.0) at the latest follow-up (Table 2). Full bone fusion was achieved in all patients (Figure 7).

Table 2
Table 2:
RA and ERD preoperatively, postoperatively, and at follow-up for thoracolumbar cases

Postoperative care

An average 1.5-day intensive care unit stay was needed for these patients, and an epidural catheter was inserted for drainage. Patients were allowed out of bed with a custom-made plastic thoracolumbosacral orthosis (TLSO) during the second postoperative week. The TLSO was kept in place for 4 months.

DISCUSSION

In the present study we successfully corrected the severe post-traumatic kyphosis in thoracolumbar region from a preoperative ERD of 60° or more to a basically normal orientation by a single-staged posterior VCR. The outcome was satisfactory and inspiring. The complications that occurred were moderate and nonspecific, which suggested that this procedure was relatively safe and should be encouraged as a choice for treatment of severe post-traumatic kyphosis.

Post-traumatic kyphosis may induce severe chronic disability and pain. Progressive deformity, neurological damage or increasing neurological deficits are the main indications for surgery.7,8 In the presence of a kyphotic deformity, compression of the neural elements are typically anterior, and the traditional approach to decompression was to use an anterior approach corpectomy. This direct approach provides easier access and allows easy placement of anterior structural support. Neurological recovery has been reported after anterior decompression procedures, but a more recent review of the literature does not support this finding, and it would appear that partial neurological deficits have the potential to be resolved irrespective of the approach used.9 Although it appears that an anterior approach is not mandatory when performing surgery for an increasing neurological deficit, it is essential to perform a thorough decompression of the neural elements and remove all the bone fragments and endplate from the posterior vertebral body that are impinging on the spinal cord.

Injuries that severely disrupt the posterior ligamentous structures can make nonoperative management or inadequate surgical treatment fail and result in delayed post-traumatic kyphosis. Under direct force, the anterior and middle columns of injured vertebra are not strong enough to afford weight bearing and there is a tendency to gradually collapse. Aging can weaken posterior muscle strength, and disc collapse can also worsen the situation.10 In addition, many patients who had undergone surgical interventions could also develop progressive kyphosis.

Laminectomy must be used with caution in the thoracolumbar spine. Another cause of postoperative failure is surgical fusion of inadequate length. Unrecognized bony elements of ligamentous injuries at adjacent levels to the primary site may be further destabilized through increased segmental loading from the short fusion. Failures in spinal fixation can result in a propagating deformity, including pedicle screw breakage, rod fracture, and screw or hook pullout. In a recent radiological study, among post-traumatic kyphosis patients, 94% patients complained about continuous back pain or lower extremity pain, in 46% kyphosis got worse, and instability was found in 36% of patients.11 Surgical treatment is aimed at correcting the kyphosis and achieving spinal cord decompression, decreasing back pain and improving neurological function.12,13

The kyphosis deformity is often associated with pain. The pain may emanate from the site of the deformity itself, the injured disc level, a bony nonunion, or from the lordotic compensation above or below the deformity site where added stresses are placed on the respective facet joints. In patients with associated neurological complications, post-traumatic tethered cord(s), due to dural adhesions, myelo-degeneration and post-traumatic syringomyelia can cause severe pain. Often the precise origin of pain is difficult to identify.

The kyphosis is often fixed and rigid, making correction difficult. In the presence of healed and contracted anterior soft tissue, surgical correction by posterior spinal decompression and fusion alone is not sufficient for the angular post-traumatic kyphosis.14 The spinal cord cannot be adequately decompressed through the posterior traditional lamina decompression because the offending compression is located anteriorly.15,16 If surgery is restricted to an anterior approach, correction of a deformity is often hindered by posterior structures. This makes the surgical techniques for correcting the deformity difficult and controversial.2,11,14,17,18 In the cases of an apparent malunion after a prior surgical intervention, if a pseudarthrosis is suspected, the fusion mass should be evaluated with a hyperextension lateral X-ray film and a CT scan. If a pseudarthrosis is observed, then a combined anterior/posterior revision procedure or a posterior approach with anterior interbody fusion should be considered to increase the chances of a successful union.

The combination of circum spinal decompression and safe correction of the vertebral column in a single posterior approach was advocated by Heinig, who described a closing wedge osteotomy. This procedure was later modified by Gertzbein and Harris17 for the correction of post-traumatic kyphosis, and an average 30° sagittal correction can be achieved by means of a wedge osteotomy and using the Harrington system. Kawahara et al18 described a technique of circum spinal decompression and a correction osteotomy using a single posterior approach for the correction of angular kyphotic deformity. Anterior decompression of the spinal cord is possible by costotransversectomy. Patients with or without neurological deficits are included as suitable candidates for the procedure. Wu et al19 also reported single-staged posterior decancelation osteotomy in rigid post-traumatic kyphosis patients, with an average 38.8° correction, and no obvious neural injury was reported. Suk et al20 compared the surgical results between combined anterior-posterior procedures and posterior closing wedge osteotomy in post-traumatic kyphosis patients. They believe that one stage single posterior PSO may achieve a larger correction, with shorter operative time and less blood loss compared with anterior-posterior surgery.

Nevertheless, a PSO corrects focal kyphosis without lengthening the anterior column; it has an axis of correction through the anterior margin of the vertebral body and leads to shortening of the posterior column. It can only be expected to achieve a less than 40° correction. How to correct the severe post-traumatic kyphosis patient with an ERD of 60° or more? Resection of a wedge shaped compressed vertebra alone cannot supply enough space for kyphotic deformity correction. Combined dorsal decompression and fixation and ventral osteotomy and grafting, a two-stage supine-prone or a three-stage supine-prone-supine procedure may be the choice. However, an approach with more incisions has related complications and more blood loss that limits these combined techniques. For a case whose local sharp angulation is beyond 60°, only by removing the upper and lower adjacent disc can the operation space be enlarged, and more correction and safer control be expected. Therefore, we used posterior VCR. This procedure has many advantages over the other surgeries mentioned above in treating post-traumatic kyphosis besides providing greater correction at a single vertebral level. When closing the wedge-shaped space created by extensive resection in this procedure, the pivot locates at the middle or posterior part of the space. Accordingly, a relatively sufficient space will simultaneously emerge anteriorly, which makes it possible to insert an anterior support device, such as an autologous iliac bone or a cage, for restoring normal sagittal alignment. Thus, the incidences of subluxation, residual dorsal impingement, and dural buckling at or near the osteotomy site can be effectively reduced by this technique. Moreover, it yields bony apposition anteriorly and posteriorly, providing greater stability and potential for bony union. The resection can even be done asymmetrically in case of asymmetric traumatic injuries so that both sagittal and coronal correction can be achieved.

In conclusion, posterior vertebral column resection can satisfactorily correct severe post-traumatic kyphosis in thoracolumbar region. Nevertheless, this challenging procedure is recommended to be performed by experienced spinal surgeon to minimize the incidence of potential complications.

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Keywords:

post-traumatic kyphosis; vertebra column resection; osteotomy

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